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A novel technique for the controlled fabrication of π-conjugated oligomers bonded to a substrate is presented. On a gold substrate, monolayers of small monomeric organic units are alternately deposited from solution. They order and connect to the previous layer by self-assembly. In each deposition step, chemisorption takes place on top of the previous monolayer through a condensation reaction. The oligomer chain growth has been analyzed by scanning tunneling microscopy, ellipsometry, and X-ray photoelectron spectroscopy. The azomethine molecules order approximately perpendicular to the gold surface. This growth process allows for flexible preparation of a range of oligomers in a self-assembled monolayer with variable electronic properties.

We have developed a process using electron beam lithography and reactive ion etching for the high resolution pattern transfer of GaN. 150 nm dots have been fabricated in GaN successfully. Photoluminescence, scanning electron microscopy, and x-ray photoelectron spectroscopy have been employed to compare the damage inflicted on the GaN surfaces after SF 6 and Ar plasma exposures. Near-band-edge luminescence analysis indicates the existence of a higher concentration of donors on the top 100 nm of the GaN surface after Ar as supposed to SF 6 plasma exposure. An order of magnitude decrease in the ratio of the yellow to the band-edge luminescence intensity is found in the samples subjected to lower ion energies. Formation of pits is observed on the substrate surfaces after plasma treatment. Nitrogen deficient surfaces limited to the top few monolayers, as well as defect propagation down to 100 nm, exist in our plasma exposed GaN samples.

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